浅谈压力容器的疲劳分析设计

随着工业的迅速发展,压力容器承受循环载荷的情况日益增多,产生疲劳失效事故的可能性也在增加,压力容器的疲劳分析设计越来越引起了人们的关注和重视。笔者以D-06A/B干燥器为实例,简要叙述了压力容器疲劳分析设计中的载荷和结构分析、应力计算、交变应力强度幅的求取、设计疲劳曲线的应用、疲劳强度校核等主要步骤及实施要点和注意事项。

大学生心理压力调查及影响因素分析

[目的]调查大学生心理压力及原因。[方法]采用疲劳与压力检测系统和大学生压力量表对江苏某大学825名本科生进行调查。[结果]大学生压力均处于轻度水平,男生压力均略高于女生,贫困生压力均高于非贫困生;不同专业的大学生主客观压力分布不同(P<0.05)。[结论]大学生心理压力处于轻度水平,不同类别大学生压力存在差异,学校应采取相关措施预防大学生心身疾病的发生。

基于智能假人压力测试系统的服装压性能测试与评价

为了标准化实验室检测压力服装的压力性能,研发一套智能假人服装压力测试系统,系统包括9个分别嵌在假人模型体表的压力传感器,用于实时监测假人各部位服装压力值。智能假人分别穿着2种弹性经编面料制作的12种规格样衣,测试连续穿着4、12 h过程中的服装压力值,分析样衣的压力性能,并提出评价压力服装的压力疲劳性能指标。研究结果表明:同种规格样衣,面料不同,压力分布有明显差异;在多数测试区域,服装压力值随着面料伸长率的增加而增大;连续穿着4 h时的服装压力疲劳度可用于表征服装压疲劳性能;面料1和面料2制作的样衣压力疲劳度分别为3%~5%和3%~9%。

地下CNG储气井疲劳寿命监测系统的研发

在理论研究构建的储气井疲劳寿命分析过程的基础上,采用VB6.0研发了一个地下CNG储气井疲劳寿命监测系统。该系统在西安某加气站上的实际应用结果表明它可实现高、中、低压储气井的疲劳寿命实时监测、分析和预警,并能指导储气井的优化运行。

发动机散热器压力载荷失效分析

汽车发动机冷却模块是发动机子系统之一。其主要部件,发动机散热器的作用是保持发动机运转在合适的温度范围内、保证运动机构正常摩擦并减少污染物排放。文章以散热器压力循环试验作为研究工况,阐述了研究纯压力载荷疲劳失效的流程,构建了散热器数字模型,介绍了由散热器数字模型转化为有限元模型的前处理过程,详细分析了仿真计算结果,完成了失效分析。

Numerical analysis of ultimate strength of concrete filled steel tubular arch bridges

The calculation of ultimate bearing capacity is a significant issue in the design of Concrete Filled Steel Tubular (CFST) arch bridges. Based on the space beam theory, this paper provides a calculation method for determining the ultimate strength of CFST structures. The accuracy of this method and the applicability of the stress-strain relationships were validated by comparing different existing confined concrete uniaxial constitutive relationships and experimental results. Comparison of these results indicated that this method using the confined concrete uniaxial stress-strain relationships can be used to calculate the ultimate strength and CFST behavior with satisfactory accuracy. The calculation results are stable and seldom affected by concrete con-stitutive relationships. The method is therefore valuable in the practice of engineering design. Finally, the ultimate strength of an arch bridge with span of 330 m was investigated by the proposed method and the nonlinear behavior was discussed.

Study of vehicle accident reconstruction based on the information of the tire marks

The tire mark is the important legacy information left at the accident scene. Based on the vehicle collision dynamics model, this study provided an optimized algorithm with vehicle final location and other related information for the tire marks. When the tire marks simulation results fit the real one well, the state of vehicle can be understood as the real state in the accident. Based on above, the vehicle velocity and direction are decided. According to the velocity and direction of the vehicle, the complete accident process can be simulated. With the help of the Pc-Crash software, the method has been applied in typical collision accident cases analysis. The reconstruction results will provide the scientific and numerical references for vehicle collision accidents analyzing and appraising.

不同非金属材料紧固力矩值研究

针对被紧固材料为非金属材料时,螺钉紧固力矩问题进行了详细的分析与试验研究。测试了多种电气设备中常用的非金属材料受到压力时的疲劳曲线,并根据螺钉紧固力矩与预紧力的关系计算得到非金属材料的最大紧固力矩值,按照一定的安全系数计算非金属材料的安全紧固力矩值,这些紧固力矩值可以作为工程应用中的重要参考依据。

Influence of Carbonation on Mechanical Properties of Concrete

As one of the most important factors that determine the lifespan of a reinforced concrete structure, carbonation not only corrodes the reinforcing steel, but also changes the mechanical properties of concrete. For better understanding the performance of carbonated concrete structure, it is necessary to study the mechanical properties of carbonated concrete. The strees strain relationship of carbonated concrete was analyzed on the basis of experiments. The specimens were made by means of accelerated carbonation and then compressed on the testing machine. Some very important characteristics of carbonated concrete were revealed by the testing results. In addition, a useful constitutive model of carbonated concrete, which proved to be suitable for analyzing carbonated concrete members, was established in this research.

A generalized plane strain theory for transversely isotropic piezoelectric plates

Study of generalized plane strain has so far been limited to elasticity. The present is aimed at parallel development of transversely isotropic piezoelasticity. By assuming that the along depth distribution of electric potential is linear, and that com- monly used Kane-Mindlin kinematical assumption is valid, two dimensional solution systems were deduced, for which, explicit solutions of the out-of-plane constraint factor, as well as the stress resultant concentration factor around a circular hole in a transversely isotropic piezoelectric plate subjected to remote biaxial tension are obtained. Comparisons of these formulas with their counterparts for elastic case yielded suggestions that whether the piezoelectric effect exacerbates or mitigates the stress resultant concentration greatly depends on material properties, particularly, the piezoelectric coefficients; the effect of plate thickness was extensively investigated.

Fatigue behavior and cumulative damage rule of concrete under cycli ccompression with constant confined stress

The effects of different lateral confinement stress on the fatigue behavior and cumulative damage of plain concrete were investigated experimentally. Eighty 100mm×100mm×100mm specimens of ordinary strength concrete were tested with constant-or variable-amplitude cyclic compression and lateral confinement pressure in two orthogonal directions. A fatigue equation was gained by modifying the classical Aas-Jakobsen S-N equation and used for taking into account the effect of the confined stress on fatigue strength of plain concrete. The present study indicates that the fatigue failure is greatly influenced by the sequence of applied variable-amplitude fatigue loading, and Miner’s rule is inapplicable to predict the residual fatigue life, especially in the sequence of low to high. The present research also shows that the exponent d of the Corten-Dolan’s damage formula is a constant depending on the materials and the levels of load spectrum, and d can be determined through the two-stage fatigue tests. The residual fatigue lives predicted by Corten-Dolan’s damage formula are found to be in good agreement with the results of the experiments.

Fatigue Crack Initiation and Propagation of Aluminum Alloy Bearings

Observation of fatigue crack initiation and propagation during fatigue test in ALSn20Cu bearing has been presented. Journal center orbit, oil film pressure and stress distribution in alloy layer have been calculated and are taken as the basis for theoretically simulating the bearing fatigue process. It is found that the calculated results are in good accordance with the experimental results, which provides a feasible way for investigation of fatigue crack propagation process in the bearing.

IEC 60335-2-34 6.0版和5.2版的主要差异解读

IEC 60335-2-34《家用和类似用途电器的安全电动机-压缩机的特殊要求》6.0版本已经正式发布,新标准中的试验测试内容和方法做了较大改变。现分析了IEC 60335-2-34最新标准6.0版和上一版本5.2版的主要差异,详细阐述了标准测试方法的新要求,供电动机-压缩机企业和检测机构的测试人员及设计人员提供参考。

Fatigue Magnification Factors of Arc-Soft-Toe Bracket Joints

Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.

Unified modeling of high temperature deformations of a Ni-based polycrystalline wrought superalloy under tension-compression, cyclic, creep and creep-fatigue loadings

The complex deformation behaviors under tension-compression, cyclic, creep and creep-fatigue loadings of a nickel-base polycrystalline wrought superalloy at 650℃ and 700℃ were experimentally investigated. To uniformly simulate the complex deformation behaviors, the modified viscoplastic constitutive model combined with both the Kachanov damage evolution equation and the Ohno-Wang modification was formulated on the basis of the Chaboche theory. The simulated results on ten-sion-compression behavior, cyclic viscoplastic and creep deformations showed comprehensive predicting ability. With the obtained material parameters, the deformations in creep-fatigue interaction under three dwell types were simulated and the capability of the modified model was further verified with good accuracy.